Array microphone and sound collection method

ABSTRACT

A sound collection method includes estimating at least one sound source direction and forming a plurality of sound collection beams in the estimated plurality of sound source direction, using sound collection signals of a plurality of microphones. The number of sound source directions estimated is smaller than the number of sound collection beams formed.

CROSS REFERENCE TO RELATED APPLICATIONS

This Nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application No. 2018-200307 filed in Japan on Oct. 24, 2018the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

A preferred embodiment according to the present invention relates to anarray microphone including a plurality of microphones, and a soundcollection method.

2. Description of the Related Art

The U.S. Pat. No. 9,894,434 discloses a tracking array microphone thatforms one sound collection beam and causes the direction of the soundcollection beam to track a direction of a sound source.

In addition, the U.S. Pat. No. 9,565,493 and the U.S. Pat. No. 9,264,553disclose an array microphone that forms a plurality of sound collectionbeams.

In the tracking array microphone that forms one sound collection beam,as disclosed in the U.S. Pat. No. 9,894,434, a time lag occurs from whena talker is changed to when the direction of the sound collection beamis changed. Therefore, the beginning of an utterance of a new talker maybe unable to be collected.

SUMMARY OF THE INVENTION

An object of a preferred embodiment of the present invention is toprovide an array microphone and a sound collection method that arecapable of supporting a plurality of sound source directions.

An array microphone according to a preferred embodiment of the presentinvention includes a plurality of microphones, an estimator thatestimates at least one sound source direction, and a beam former thatforms a plurality of sound collection beams in the estimated at leastone sound source directions, using sound collection signals of theplurality of microphones. The number of the at least one sound sourcedirection estimated by the estimator is smaller than the number of soundcollection beams formed by the beam former.

The above and other elements, features, characteristics, and advantagesof the present invention will become more apparent from the followingdetailed description of the preferred embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of the interior of a room in which anarray microphone 1 is installed.

FIG. 2 is a plan view of the interior of the room in which the arraymicrophone 1 is installed.

FIG. 3A is a block diagram showing an example of a configuration of thearray microphone 1, and FIG. 3B is a block diagram showing anotherexample of the array microphone 1 of FIG. 3A.

FIG. 4 is a flow chart showing an operation of the array microphone 1.

FIG. 5 is a bottom view of the array microphone 1.

FIG. 6 is a block diagram showing a functional configuration of a beamformer 21.

FIG. 7 is a plan view of the interior of a room in which the arraymicrophone 1 is installed.

FIG. 8 is a plan view of the interior of a room in which the arraymicrophone 1 is installed.

FIG. 9 is a plan view of the interior of a room in which the arraymicrophone 1 is installed.

FIG. 10 is a block diagram showing a configuration of an arraymicrophone 1A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An array microphone according to the present preferred embodimentincludes a plurality of microphones, an estimator that estimates atleast one sound source direction, and a beam former that forms aplurality of sound collection beams in the estimated at least one soundsource directions, using sound collection signals of the plurality ofmicrophones. The number of the at least one sound source directionestimated by the estimator is smaller than the number of soundcollection beams formed by the beam former.

In this manner, the array microphone causes the number of soundcollection beams to be greater than the estimation number of soundsource directions, and directs the sound collection beams in a directionin addition to the currently estimated sound source direction.Accordingly, the array microphone, even when a talker is changed, isable to collect an utterance of a new talker by the sound collectionbeam that has been already directed in another direction. Therefore, thearray microphone is able to support a plurality of sound sourcedirections, and is also able to collect the beginning of an utterance ofa new talker. In addition, an increase in the amount of calculation isable to be reduced more by reducing the estimation number of soundsource directions than by estimating a plurality of sound sourcedirections and forming a plurality of sound collection beams in eachdirection.

In addition, the array microphone may include a plurality ofmicrophones, an estimator that estimates a direction of at least twosound sources, and a beam former that forms at least two soundcollection beams in the direction of at least two sound sources that hasbeen estimated by the estimator, using sound collection signals of theplurality of microphones. In such a case, the estimator may estimate atwo-dimensional direction (the plane direction and the elevationdirection). In this case, the array microphone is able to form a soundcollection beam that tracks at least two sound sources, and is able toautomatically and clearly collect sound of the at least two soundsources. Therefore, the array microphone is able to support a pluralityof sound source directions. As a matter of course, the array microphoneis also able to support 0 or 1 sound source direction.

In addition, the array microphone may include a mixing processor thatmixes an audio signal according to a sound collection beam, among theplurality of sound collection beams, by a gain according to volume ofthe sound collection beam.

In such a case, since the gain of the sound collection beam directed toa direction other than the currently estimated sound source direction isreduced, the voice of a current talker is able to be clearly collected.

Hereinafter, a specific configuration according to the present preferredembodiment will be described. FIG. 1 is an elevational view of aninterior of a room in which an array microphone 1 is installed, and FIG.2 is a plan view of the interior of the room in which the arraymicrophone 1 is installed.

The array microphone 1 is installed on a ceiling 60 in a room. Aconference desk T1 is installed directly under the array microphone 1.In the example of FIG. 1 and FIG. 2, a plurality of users (talkers): auser h1, a user h2, a user h3, and a user h4 are present around theconference desk T1. The array microphone 1 has a housing having a thinrectangular parallelepiped shape. In the example of FIG. 1, the topsurface of the array microphone 1 is installed on the ceiling 60. It isto be noted that the array microphone 1 may be hung from the ceiling 60,for example. In addition, the array microphone 1 may be configured as aceiling tile. Moreover, the array microphone 1 may be provided asinterior equipment or may be configured to be replaceable. In a case inwhich the array microphone 1 is installed as a ceiling tile, the ceilingtile is configured to be replaceable. In addition, although the arraymicrophone 1 according to the present preferred embodiment is installedon the ceiling 60, the array microphone 1 does not necessarily need tobe installed on the ceiling 60. For example, the array microphone 1 maybe installed on a wall surface, a desk top, a floor, or the like.

FIG. 3A is a block diagram showing an example of a configuration of thearray microphone 1. FIG. 3B is a block diagram showing a configurationof another example of the array microphone 1. The array microphone 1, asshown in FIG. 3A, includes a plurality of microphones 11-1 to 11-n, abeam former 21, an auto mixer (AUTOMIX) 31, an interface (I/F) 41, and asound source direction estimator 25. FIG. 4 is a flow chart showing anoperation of the array microphone 1.

Each of the beam former 21, the AUTOMIX 31, and the sound sourcedirection estimator 25 may be configured by hardware or may beconfigured by software such as the beam forming module, the AUTOMIXmodule and the sound source direction estimating module, as shown inFIG. 3B. A processor such as a CPU 12 reads and performs software storedin a storage medium such as a memory 13. The CPU 12 performs the samefunction as the beam former 21 by executing the beamforming module. TheCPU 12 performs the same function as the AUTOMIX 31 by executing theAUTOMIX module. The CPU 12 performs the same function as the soundsource direction estimator 25 by executing the sound source directionestimating module. It is to be noted that the software does not need tobe stored in the memory 13 or the like of the array microphone 1 and maybe downloaded each time from another device such as a server andexecuted. When each of the beam former 21, the AUTOMIX 31, and the soundsource direction estimator 25 is configured by software, each of CPU12and memory 13 may be plural.

The plurality of microphones 11-1 to 11-n are installed on the bottomsurface of the housing of the array microphone 1. The sound collectiondirection of the plurality of microphones 11-1 to 11-n is directeddownward of the array microphone 1.

FIG. 5 is a view when the array microphone 1 is viewed from the side ofthe bottom surface. The large number of circles shown in FIG. 5represent the plurality of microphones 11-1 to 11-n. The plurality ofmicrophones 11-1 to 11-n, as shown in FIG. 5, configure an arraymicrophone arranged in a plane. However, the arrangement of theplurality of microphones 11-1 to 11-n is not limited to the exampleshown in FIG. 5. It is to be noted that the plurality of microphones11-1 to 11-n may be non-directional microphones or may be directionalmicrophones.

As shown in FIG. 3A, an audio signal (hereinafter referred to as a soundcollection signal) that has been collected by each of the plurality ofmicrophones 11-1 to 11-n is inputted to the beam former 21. The beamformer 21 delays sound collection signals of the plurality ofmicrophones 11-1 to 11-n with a predetermined amount of delay andcombines the sound collection signals. As a result, the beam former 21forms a sound collection beam having strong sensitivity in apredetermined direction. The beam former 21 is able to form a pluralityof sound collection beams. In the example of the present preferredembodiment, the beam former 21 forms four sound collection beams (afirst sound collection beam b1, a second sound collection beam b2, athird sound collection beam b3, and a fourth sound collection beam b4)at the maximum (see FIG. 2). The number of sound collection beams andthe direction of each sound collection beam are determined based on asound source direction that has been estimated by the sound sourcedirection estimator 25.

The sound collection signals according to the sound collection beams areinputted to the AUTOMIX 31. The AUTOMIX 31 corresponds to the mixingprocessor of the present invention. The AUTOMIX 31 mixes the soundcollection signals according to the sound collection beams by a gainaccording to the volume of each of the sound collection beams. As aresult, the sound collection beam of which the volume is high isemphasized, so that the array microphone 1 is able to clearly obtain thevoice of a current talker. However, in the present invention, theAUTOMIX 31 is not an essential configuration.

The audio signal mixed by the AUTOMIX 31 is inputted to the I/F 41. TheI/F 41 is a communication I/F such as a USB, for example. The I/F 41encodes an inputted audio signal into a predetermined data format, andtransmits an encoded signal to another device such as a personalcomputer. As a result, the array microphone 1 is able to transmit thecollected sound to a device at a remote place, and is able to achieve ateleconference. It is to be noted that the I/F 41 may receive an audiosignal from the device at a remote place. The I/F 41 outputs a receivedaudio signal to a not-shown speaker. As a result, a conferenceparticipant can hear a sound of a remote place.

The sound source direction estimator 25 estimates a sound sourcedirection using an audio signal of a plurality of microphones (S11 shownin the flow chart of FIG. 4). The sound source direction estimator 25estimates a sound source direction by calculating the cross correlationof the sound collection signal of the plurality of microphones, forexample. The sound source direction estimator 25, by obtaining the peakof the cross correlation of the sound collection signals of certain twomicrophones, for example, is able to obtain a direction of a soundsource with respect to these two microphones. Furthermore, the soundsource direction estimator 25, by obtaining the peak of the crosscorrelation of the sound collection signals of two differentmicrophones, is able to obtain a direction of a sound source withrespect to these two different microphones. The sound source directionestimator 25 estimates a sound source direction based on a plurality ofcross correlation peaks calculated in this manner.

Only the estimation of the sound source direction by the two microphonesis able to estimate only a one-dimensional direction (a plane directionor an elevation direction, for example). Alternatively, only theestimation of the sound source direction by the two microphones is ableto estimate only a one-dimensional direction and a distance to a soundsource. However, the sound source direction estimator 25, from the arraymicrophone arranged in a plane, selects two or more sets of a pluralityof microphones, and obtains a plurality of cross correlation peaks. As aresult, the sound source direction estimator 25 estimates atwo-dimensional direction (the plane direction and the elevationdirection). Moreover, the sound source direction estimator 25, inaddition to the two-dimensional direction, is also able to estimate adistance to a sound source.

In addition, the number of sound sources to be estimated and theestimation accuracy improve as the number of microphones and the numberof cross correlations to be calculated increase. The sound sourcedirection estimator 25 according to the present preferred embodimentestimates two sound source directions. In other words, the sound sourcedirection estimator 25 estimates two sound source directions byobtaining two more peaks (two peaks from the high level) of each crosscorrelation.

It is to be noted that the method of estimating a sound source directionis not limited to the above example. The sound source directionestimator 25 is also able to estimate a sound source direction, forexample, by comparing the levels of the sound collection beams in aplurality of directions, the sound collection beams being formed by thebeam former 21. In such a case, the beam former 21 forms a soundcollection beam in a plurality of directions (1000 directions, forexample) in a room in advance. The sound source direction estimator 25obtains the level of each of the sound collection beams in the pluralityof directions. The sound source direction estimator 25 obtains spatiallevel distribution of the sound collection beams in the plurality ofdirections. The sound source direction estimator 25 estimates aplurality of directions of a sound source based on the leveldistribution.

However, as described above, in a case in which a large number (1000directions, for example) of sound collection beams are formed andspatial level distribution is obtained, the amount of calculation isextremely large. In addition, in a case in which a sound sourcedirection is estimated based on the peak of cross correlation, it isdifficult to estimate a large number of sound source directions.Accordingly, the array microphone 1 according to the present preferredembodiment, in order to reduce the amount of calculation, by causing thenumber of sound collection beams to be greater than the estimationnumber of sound source directions while reducing the estimation numberof sound source directions, supports a large number of sound sources.

The beam former 21 controls the number and direction of sound collectionbeams based on the sound source direction that the sound sourcedirection estimator 25 has estimated. FIG. 6 is a block diagram showinga functional configuration of the beam former 21.

The beam former 21 functionally includes a comparing device 201, a delaycalculator 202, a delayer 203-1, a delayer 203-2, a delayer 203-3, and adelayer 203-4. The delayer 203-1 includes a delay device 251-1 to adelay device 251-n, and an adder 255. The delayer 203-1, the delayer203-2, the delayer 203-3, and the delayer 203-4 each have the sameconfiguration.

Each functional configuration of the beam former 21 is achieved whenhardware such as the CPU 12 or a DSP that configures the beam former 21reads and executes a program from the memory 13.

The comparing device 201 receives an input of information on the soundsource direction that the sound source direction estimator 25 hasestimated. In this example, the comparing device 201 receives an inputof information that indicates a first sound source direction d1 and aninput of information that indicates a second sound source direction d2.The information that indicates the first sound source direction d1includes an angle θ1 around a vertical axis that indicates the planedirection and an angle Φ1 around a horizontal axis that indicates theelevation direction. The information that indicates the second soundsource direction d2 includes an angle θ2 around the vertical axis and anangle Φ2 around the horizontal axis. The angle around the vertical axis,as shown in FIG. 2, is represented by the relative angle on the basis ofa predetermined direction (the right direction in FIG. 2) in a plan viewof the housing of the array microphone 1. The angle around thehorizontal axis, as shown in FIG. 1, is represented by the relativeangle on the basis of a predetermined direction (the right direction inFIG. 1) in an elevation view of the housing of the array microphone 1.

The comparing device 201 determines the number and direction of soundcollection beams based on the first sound source direction d1 and thesecond sound source direction d2 that have been inputted from the soundsource direction estimator 25. In the present preferred embodiment, foursound collection beams are formed at the maximum. Accordingly, thecomparing device 201 sets the direction of the first sound collectionbeam b1 to the angle θ-1 and the angle Φ-1, sets the direction of thesecond sound collection beam b2 to the angle θ-2 and the angle Φ-2, setsthe direction of the third sound collection beam b3 to the angle θ-3 andthe angle Φ-3, and sets the direction of the fourth sound collectionbeam b4 to the angle θ-4 and the angle Φ-4.

The comparing device 201 transmits angle information on each set soundcollection beam to the delay calculator 202. The delay calculator 202,based on the angle information on each received sound collection beam,calculates the amount of delays of each of the delay device 251-1 to thedelay device 251-n in each of the delayer 203-1, the delayer 203-2, thedelayer 203-3, and the delayer 203-4. Then, the delay calculator 202sets the amount of delays of each of the delay device 251-1 to the delaydevice 251-n in each of the delayer 203-1, the delayer 203-2, thedelayer 203-3, and the delayer 203-4. Each of the delay device 251-1 tothe delay device 251-n in each of the delayer 203-1, the delayer 203-2,the delayer 203-3, and the delayer 203-4 delays an inputted soundcollection signal, and outputs the delayed sound collection signal tothe adder 255. The adder 255 forms a sound collection beam by combiningthese sound collection signals. The sound collection beam that has beenformed is outputted to the AUTOMIX 31.

The comparing device 201 stores the angle information on each currentsound collection beam in the memory 13. The comparing device 201compares the angle of the first sound source direction d1 and the secondsound source direction d2, and the angle of each current soundcollection beam (S12 shown in the flow chart of FIG. 4).

The comparing device 201 determines whether or not a sound collectionbeam is present within a predetermined angle range with respect to eachof the first sound source direction d1 and the second sound sourcedirection d2 (S13). The comparing device 201 determines whether or not asound collection beam is present within the range of the angle θ1±5degrees and the angle Φ1±5 degrees, for example. The comparing device201, in a case of determining that a sound collection beam is presentwithin the predetermined angle range in both the first sound sourcedirection d1 and the second sound source direction d2, skips thesubsequent processing. As a result, the setting of the current soundcollection beam is maintained.

The comparing device 201, in a case of determining that a soundcollection beam is not present within the predetermined angle range ineither the first sound source direction d1 or the second sound sourcedirection d2, determines whether or not the current number of beamsreaches the maximum number (S14). In this example, the maximum number ofsound collection beams is four. Accordingly, the comparing device 201determines whether or not four sound collection beams are beingcurrently formed.

The comparing device 201, in a case of determining that three or lesssound collection beams are being currently formed, forms a new soundcollection beam (S15). The comparing device 201 sets the direction ofthe new sound collection beam to the first sound source direction d1 orthe second sound source direction d2. For example, the comparing device201, in a case of determining that a sound collection beam is notpresent within the range of the angle θ1±5 degrees and the angle Φ1±5degrees when the current number of sound collection beams is three, setsthe angle θ-4 and the angle Φ-4 of the fourth sound collection beam b4to the angle θ1 and the angle Φ1. As a result, the new fourth soundcollection beam b4 is directed in the sound source direction.

In addition, the comparing device 201, in a case of determining thatfour sound collection beams are being currently formed, updates theangle of the earliest updated sound collection beam (S16).

The plan views of FIG. 7 and FIG. 8 are views illustrating a case inwhich the talker h1 ends an utterance and the talker h2 and a new talkerh5 issue an utterance, as an example.

The sound source direction estimator 25 estimates the first sound sourcedirection d1 in a direction of the talker h5. In addition, the soundsource direction estimator 25 estimates the second sound sourcedirection d2 in a direction of the talker h2. In such a case, thecomparing device 201 determines that a sound collection beam is notpresent within the predetermined angle (within the range of the angleθ1±5 degrees and the angle Φ1±5 degrees, for example) of the first soundsource direction d1. Then, as shown in the plan view of FIG. 8, thecomparing device 201, in a case in which the earliest updated soundcollection beam is the third sound collection beam, for example, setsthe angle θ-3 and the angle Φ-3 of the third sound collection beam b3 tothe angle θ1 and the angle Φ1. As a result, the third sound collectionbeam b3 is directed in the direction of the talker h5.

Even when the talker h5 ends the utterance and the talker h1 resumes anutterance, the first sound collection beam b1 is directed in thedirection of the talker h1, so that the array microphone 1 is able tocollect sound without lacking the beginning of the utterance of thetalker h1.

In this manner, the array microphone 1 causes the number of soundcollection beams to be greater than the estimation number of soundsource directions, and directs the sound collection beams in a directionin addition to the currently estimated sound source direction.Accordingly, the array microphone 1, even when a talker is changed, isable to collect an utterance of a new talker by the sound collectionbeam that has been already directed in another direction. Therefore, thearray microphone 1 is able to collect the beginning of an utterance of anew talker while reducing the amount of calculation.

It is to be noted that a sound collection beam to be updated is notlimited to the earliest updated sound collection beam. For example, thecomparing device 201 may update a sound collection beam of which theangle is closest to the estimated sound source direction.

In addition, the comparing device 201 may assign an area to each soundcollection beam. For example, as shown in FIG. 9, the comparing device201, in a plan view of the interior of the room, sets four areas. Then,the comparing device 201 sets an area (Area 1) assigned to the firstsound collection beam, an area (Area 2) assigned to the second soundcollection beam, an area (Area 3) assigned to the third sound collectionbeam, and an area (Area 4) assigned to the fourth sound collection beam.The comparing device 201 determines an area to which the estimated soundsource direction belongs, and updates the angle of a corresponding soundcollection beam.

Alternatively, the comparing device 201 may record the estimatedfrequency of the sound source direction for each area, and may determinethe sound collection beam to be updated according to the estimatedfrequency. For example, in a case in which the estimated frequency inthe sound source direction is high in the Area 1, and the estimatedfrequency in the sound source direction is low in the Area 3, thecomparing device 201 may set the angle of the third sound collectionbeam assigned to the Area 3 to direct in the direction of the Area 1.

In addition, the sound collection direction of at least one soundcollection beam among the plurality of sound collection beams may befixed. A user may manually set and fix the direction of the soundcollection beam. For example, in a case in which it is known in advancethat a talker such as a chairperson with a high utterance frequency ispresent, the user sets the direction of a sound collection beam to thedirection of the chairperson. As a result, the array microphone 1 isable to appropriately collect the beginning of an utterance whilefurther reducing the amount of calculation.

Subsequently, FIG. 10 is a block diagram showing a configuration of anarray microphone 1A further including an echo canceller. The samereference numerals are used to refer to components common to the arraymicrophone 1 shown in FIG. 3A, and the description will be omitted. Thearray microphone 1A of FIG. 10 includes a beam former 21, an AEC (anecho canceller) 50-1, an AEC 50-2, an AEC 50-3, and an AEC 50-4 that areconnected to the AUTOMIX 31. In addition, the array microphone 1Aincludes an AEC 51-1, an AEC 51-2, an AEC 51-3, and an AEC 51-4 each ofwhich is connected to the sound source direction estimator 25 and eitherof a plurality of microphones. The I/F 41 receives an audio signal froma device at a remote place. The I/F 41 outputs a received audio signalto the AEC 51-1, the AEC 51-2, the AEC 51-3, and the AEC 51-4. Inaddition, the I/F 41 outputs the received audio signal to the AEC 50-1,the AEC 50-2, the AEC 50-3, and the AEC 50-4.

Each of the AEC 51-1, the AEC 51-2, the AEC 51-3, and the AEC 51-4receives an input of a sound collection signal of a correspondingmicrophone, and performs processing to reduce an echo component.Specifically, each of the AEC 51-1, the AEC 51-2, the AEC 51-3, and theAEC 51-4 includes a digital filter. The AEC 51-1, the AEC 51-2, the AEC51-3, and the AEC 51-4 have a filter coefficient that simulates atransfer function from a speaker to a microphone. The AEC 51-1, the AEC51-2, the AEC 51-3, and the AEC 51-4, by performing filter processing anaudio signal received from the device at a remote place, generate apseudo echo signal that simulates an echo component. The AEC 51-1, theAEC 51-2, the AEC 51-3, and the AEC 51-4 reduce the pseudo echo signalfrom the sound collection signal of the microphone. As a result, thesound source direction estimator 25 is able to estimate a sound sourcedirection by the sound collection signal of which the echo component hasbeen reduced.

The AEC 50-1, the AEC 50-2, the AEC 50-3, and the AEC 50-4 respectivelyreceive an input of a sound collection signal according to the firstsound collection beam b 1, the second sound collection beam b2, thethird sound collection beam b3, and the fourth sound collection beam b4,and perform processing to reduce an echo component. The processing toreduce an echo component is the same as the processing of the AEC 51-1,the AEC 51-2, the AEC 51-3, and the AEC 51-4. In this manner, the arraymicrophone 1A is able to reduce the amount of calculation more byreducing an echo component from the sound collection signal according tothe sound collection beam than by reducing an echo component from thesound collection signals of all the microphones.

Finally, the foregoing preferred embodiments are illustrative in allpoints and should not be construed to limit the present invention. Thescope of the present invention is defined not by the foregoing preferredembodiment but by the following claims. Further, the scope of thepresent invention is intended to include all modifications within thescopes of the claims and within the meanings and scopes of equivalents.

What is claimed is:
 1. An array microphone comprising: a plurality ofmicrophones; an estimator that estimates at least one sound sourcedirection; and a beam former that forms a plurality of sound collectionbeams in the estimated at least one sound source directions, using soundcollection signals of the plurality of microphones, wherein a number ofthe at least one sound source direction estimated by the estimator issmaller than a number of sound collection beams formed by the beamformer.
 2. The array microphone according to claim 1, further comprisinga mixing processor that mixes an audio signal according to a soundcollection beam, among the plurality of sound collection beams, by again according to volume of the sound collection beam.
 3. The arraymicrophone according to claim 1, wherein the plurality of microphonesare arranged in a plane.
 4. The array microphone according to claim 1,wherein the plurality of microphones are configured as a ceiling tile.5. The array microphone according to claim 4, wherein the ceiling tileis configured to be replaceable.
 6. The array microphone according toclaim 1, further comprising an echo canceller that removes an echocomponent from an audio signal according to a sound collection beam,among the plurality of sound collection beams.
 7. The array microphoneaccording to claim 1, further comprising: an echo canceller that removesan echo component from the plurality of sound collection signals of theplurality of microphones, wherein the estimator estimates each soundsource direction, using the sound collection signals in which the echocomponent has been removed by the echo canceller.
 8. The arraymicrophone according to claim 1, wherein: a first sound collectiondirection of at least one sound collection beam, among the plurality ofsound collection beams, is fixed, and a second sound collectiondirection of at least one sound collection beam, among the plurality ofsound collection beams, is determined based on the sound sourcedirection thereof that has been estimated by the estimator.
 9. The arraymicrophone according to claim 1, wherein the beam former forms one soundcollection beam, among the plurality of sound collection beams, for eachpredetermined area.
 10. The array microphone according to claim 9,wherein the beam former: records an estimated frequency of the soundsource direction for each area; and forms the one sound collection beamaccording to the estimated frequency.
 11. A sound collection methodcomprising: one or more processors and memory storing one or moreprograms for execution by the one or more processors: estimating atleast one sound source direction; and forming a plurality of soundcollection beams in the estimated at least one sound source directions,using sound collection signals of a plurality of microphones, wherein anumber of sound source directions to be estimated is smaller than anumber of sound collection beams to be formed.
 12. The sound collectionmethod according to claim 11, further comprising mixing an audio signalaccording to a sound collection beam, among the plurality of soundcollection beams, by a gain according to volume of the sound collectionbeam.
 13. The sound collection method according to claim 11, wherein theplurality of microphones are configured as a ceiling tile.
 14. The soundcollection method according to claim 13, wherein the ceiling tile isconfigured to be replaceable.
 15. The sound collection method accordingto claim 11, further comprising removing an echo component from an audiosignal according to a sound collection beam, among the plurality ofsound collection beams.
 16. The sound collection method according toclaim 15, further comprising: removing an echo component from theplurality of sound collection signals of the plurality of microphones,wherein the estimating of the plurality of sound source directionsestimates each sound source direction, using the sound collectionsignals in which the echo component has been removed.
 17. The soundcollection method according to claim 11, wherein a first soundcollection direction of at least one sound collection beam, among theplurality of sound collection beams is fixed, and a second soundcollection direction of at least one sound collection beam, among theplurality of sound collection beams, is determined based on the soundsource direction thereof that has been estimated.
 18. The soundcollection method according to claim 11, wherein the forming of theplurality of sound collection beams forms one sound collection beam,among the plurality of the sound collection beams, for eachpredetermined area.
 19. The sound collection method according to claim18, wherein the forming of the plurality of sound collection beams:records an estimated frequency of the sound source direction for eacharea; and forms the one sound collection beam according to the estimatedfrequency.
 20. An array microphone comprising: a plurality ofmicrophones; one or more processors; and one or more memories havingprogram instructions stored thereon that are executable by the one ormore processors to cause the array microphone to: estimate at least onesound source direction; and form a plurality of sound collection beamsin the estimated at least one sound source directions, using soundcollection signals to be collected by the plurality of microphones,wherein a number of sound source directions to be estimated is smallerthan a number of sound collection beams to be formed.